Every year, about 75 million units of blood are collected worldwide (Klein et al., The Lancet 370: 415-426 (2007)). Units of whole blood (450-500 mL) are collected and refrigerated in plastic packs with an anti-coagulant as a preservative. Whole blood is rarely used for transfusion therapy, however, and its use is limited to massive bleeding, where erythrocytes, also referred to as red blood cells (RBCs), volume, and plasma factors are all needed for survival of the patient. Rather, plasma is removed from whole blood to provide units of RBCs (200-350 mL). Oftentimes, the plasma is replaced with a solution that improves cellular viability during storage.
The transfusion of RBCs is one of the few treatments that adequately restore tissue oxygenation. Depending on the specific indication, RBCs can be filtered, washed, frozen or irradiated.
The safety of blood products used for transfusion-based therapies has always been of great concern. To address those concerns, potential blood donors must first be screened. Initially, the potential donor is required to fill out a questionnaire to assess current and past health, recent medical procedures, recent blood donations, travel to locations with known risk factors and behaviors associated with increased risk. Current examples of such questionnaires are available from AABB—formerly known as the American Association of Blood Banks. Limitations are put on who may donate based on the answers to the questionnaire.
However, data obtained from such questionnaires are subjective in nature and have insufficient reliability to assure the safety of donated blood. Blood donation facilities must, therefore, employ further diagnostic tests that supply objective evidence that the donated blood is safe for use. Such testing may include assays that screen for transmissible infectious agents, such as viruses (e.g., hepatitis B, hepatitis C, human immunodeficiency virus (HIV), human T-lymphotropic virus, cytomegalovirus, and Epstein-Barr virus), parasites (e.g., Chagas, and malaria) and bacteria. The screening of donors and blood products for infectious diseases has dramatically reduced the risk of infection from blood transfusion in developed countries; however, infection remains a major risk in developing countries, where 13 million units of blood are not tested for HIV, hepatitis viruses, and the like (Klein et al. (2007), supra). While pathogen inactivation techniques for RBCs are currently in clinical trials, none is available for use as of yet (Klein et al. (2007), supra).
It is further recognized that donor blood immunologic factors may present a safety hazard for incompatible recipients. So-called “blood group antigens” and so-called “Rh factors” are representative of such immunologic factors, and may lead to hemolytic transfusion reactions.
Additionally, regulatory procedures have been established to define the shelf-life of donated blood and its components. Currently, RBC concentrates in CDPA-1 (citrate, dextrose, phosphate, and adenine) have a shelf-life of 35 days at 1-6° C., while RBCs packed in an additive solution can be stored for 42 days. These limitations are based on the 75% viability of the erythrocytes 24 hours after transfusion. Recent studies have indicated that these criteria may not be sufficient and that poor outcomes may result in patients transfused with RBCs older than 14 days (Koch et al., N. Eng. J. Med. 358: 1229-1239 (2008)). Some researchers have suggested that the increased risk of adverse outcomes is due to depletion of oxygen-carrying chemicals and increased cellular membrane rigidity, among others.
In addition to the above, it is known that more people die from cardiovascular disease than any other disease. Cardiovascular disease accounts for one of every two deaths in the U.S. alone.
Cardiac markers, such as cardiac proteins and cardiac enzymes, are often used in the diagnosis and prognosis of cardiovascular disease. Examples of such markers include troponin, brain natriuretic peptide (BNP), nt-proBNP, creatine kinase isoenzyme MB (CKMB), myoglobin, choline, C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor α (TNFα), placental growth factor (P/GF), pregnancy-associated plasma protein-A (PAPP-A), and soluble CD40 (sCD40). Such markers are measured in the serum or plasma fractions of blood collected from patients displaying one or more clinical symptoms of cardiovascular disease, not in the cellular fraction of blood tested, and more particularly, not in RBCs. Moreover, patients suffering from cardiovascular disease often undergo surgical intervention requiring transfusion of RBCs.
The present inventors have discovered a subpopulation of blood donors that exhibit high levels of free choline in their erythrocytes, while maintaining a normal level of free choline in plasma. Such an elevation of free choline indicates a change in erythrocyte molecular composition, cellular morphology, and biochemistry that constitutes a transmissible factor affecting cardiovascular health.
In view of the foregoing, the present disclosure seeks to provide a method of assessing whether or not erythrocytes are suitable for transfusion. The present disclosure also seeks to provide a kit for use in such a method. The method and kit can be used to screen potential blood donors and assess processed blood products before use in transfusion therapy. These and other objects and advantages, as well as other additional features, will become apparent from the detailed description provided herein.